The vast majority of patients awaiting organ transplantation have end-stage chronic liver disease secondary to cirrhosis. Hepatocyte transplantation has several important advantages over organ transplantation and was recently shown to prolong the survival and improve the physiologic abnormalities associated with cirrhosis and end-stage liver disease in rodents. The number of human livers available for hepatocyte isolation and later transplantation, however, is limited. One possible solution to the human donor availability issue is transplantation of hepatocytes from pigs. Two major concerns regarding the use of porcine hepatocytes in man relate to the degree to which xenogeneic hepatocytes can restore normal liver physiology to patients with liver dysfunction and the immunological response to liver cells or their products. Preliminary studies indicate that immunosuppression may not be needed to improve the survival or function of allogeneic rat or pig hepatocytes transplanted in cirrhotic rats. However, specific antibody and cellular immune responses to pig hepatocytes vary by species and the specific physiologic compatibility and function of pig liver proteins in man is unknown. We now propose to extend our observations in a primate model that will serve as a prelude to clinical application. The aims of this proposal are: 1) To test the degree to which porcine hepatocyte transplantation can improve liver function in cirrhotic non-human primates; 2) To examine whether pig hepatocytes are susceptible to rejection mediated by anti-swine antibodies and test whether the primate immune response to porcine hepatocytes is significantly different in cirrhotic versus non-cirrhotic recipients; and 3) To determine whether porcine hepatocyte transplantation leads to systemic complications that include a) immune complex formation, b) activation of the coagulation/complement system and c) immune sensitization that may preclude later allotransplantation.